1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel having a front substrate with a structure to improve brightness and maintain a high contrast.
2. Description of the Related Art
A plasma display panel, generally considered to be a display device that will replace conventional cathode ray tubes, obtains an image by exciting a fluorescent material arranged in a predetermined pattern with ultraviolet rays generated by a discharge gas sealed in a space formed by two substrates on which a plurality of electrodes are formed, the electrodes applying a voltage therebetween.
The plasma display panel can be divided into direct current plasma display panels and alternating current plasma display panels according to the type of discharge. At least one electrode is covered by a dielectric layer in the alternating current plasma display panel, and a discharge is performed by a field of a wall charge instead of a direct migration of charges between corresponding electrodes.
An alternating current plasma display panel comprises a front substrate on which an image is displayed and a rear substrate facing the front substrate. Pairs of X and Y electrodes are disposed on the front substrate, and address electrodes crossing the X and Y electrodes are disposed on a surface of the rear substrate facing the front substrate. The X and Y electrodes on the front substrate form a sustaining electrode pair. The sustaining electrode pair is formed of pairs of transparent electrodes, made of a material such as Indium Tin Oxide (ITO), and bus electrodes with a narrow width, formed of a metal, are disposed on a lower surface of the pairs of transparent electrodes to reduce line resistance. The sustaining electrode pair can be formed of only the bus electrodes or the transparent electrodes. The sustaining electrode pair composed of the X and Y electrodes and the crossing address electrodes form a unit discharge cell.
A front dielectric layer and a rear dielectric layer are respectively arranged on each surface of the front substrate having the X and Y electrodes and the rear substrate having the address electrodes. A protective layer of MgO is arranged on the front dielectric layer, and a plurality of barrier ribs to maintain a discharge distance and to prevent electrical and optical cross-talk between the discharge cells are arranged on the rear dielectric layer. Red, green, and blue fluorescent materials are coated on both sides of the barrier ribs and on an upper surface of the rear dielectric layer on which the barrier ribs are not arranged.
The plasma display panel having the above structure is operated in the following manner. When a discharge cell is selected, a predetermined voltage is applied to the address electrode and the Y electrode in the discharge cell to cause an address discharge between the two electrodes, and then, a wall charge is formed on the front dielectric layer. Afterwards, when a predetermined voltage is applied between the X and Y electrodes, a sustaining discharge occurs in the discharge gas due to migrating wall charges between the two electrodes, generating ultraviolet rays, and an image is displayed from the excited fluorescent material by the ultraviolet rays.
However, because the bus electrodes are not arranged in the non-discharge region of the plasma display panel, contrast is reduced due to reflection of external light infiltrated into the plasma display panel through a non-discharge region.
To solve this problem, the plasma display panel disclosed in Korean Patent Publication No. 2000-0009235, uses a light absorption reflection film arranged between the sustain electrode pairs. The light absorption reflection film, including a black material, is arranged between the discharge cells. Accordingly, the contrast increases since external light is absorbed by the light absorption reflection film in the non-discharge region. However, brightness is reduced since the light absorption reflection film absorbs visible light emitted from the discharge space because it is black. This problem becomes more severe as the width of the light absorption reflection film is increased to further increase the contrast.